1. Field of the Invention
The present invention relates to a touch sensor, a touch pad and an input device.
2. Description of the Related Art
Conventionally, a touch pad, which detects the position of the touched surface and displays the position on a display when touched by the surface, has been known in general. As such a touch pad, there are two major types; a capacitance type used for a touch pad of a personal computer or the like, and a pressure sensitive type used in a gaming machine, a personal digital assistant (PDA) or the like (e.g., refer to Japanese Patent Publication No. 2003-196007).
In addition, a technique of a touch pad, which enables easy character input even when the surface area used for character input is small, has been disclosed. The above technique has been used for cellular phone, PDA or the like. (e.g., refer to Japanese Patent Publication No. 2003-196007).
However, even though the conventional touch pad can detect a movement in the x-y plane, it cannot additionally detect a depression in the z-direction. To be more specific, the capacitance type detects a change in a surface charge of a display panel by detecting a finger touching the display panel. The capacitance type also detects a change in a capacitance caused by a finger approaching an electrode and senses whether the finger touches the display panel or not. For the pressure sensitive type, a resistive film type is widely used. The resistive film type calculates the contacted position out of a resistance value when an upper and lower electrodes of a screen contact each other caused by a finger or the like pressing the screen. Hence, it has not been easy to discriminate, for example, between dragging and moving a cursor. For this reason, heretofore, a click button has been separately provided to a touch panel, and dragging operation is achieved by using the click button and the touch pad in combination.